Question / Help Why do media sources not go to stream/recording unless set for Monitor and Output?

[Bob Denny]

I have a scene that includes a Media Source (an MP3 file), set to loop. When I select the scene, I see the green VU meter line bouncing, and I can set its Advanced Audio properties Monitor and definitely hear it (I have a separate set of headphones for monitoring, not desktop audio). However with it set to Monitor Off, and the check mark set in Tracks, it does not go to the recorded/ streamed output.

What am I missing?